Multiple figures in a single window

Question

I want to create a function which plot on screen a set of figures in a single window. By now I write this code:

import pylab as pl

def plot_figures(figures):
    """Plot a dictionary of figures.

    Parameters
    ----------
    figures : <title, figure> dictionary

    """
    for title in figures:
        pl.figure()
        pl.imshow(figures[title])
        pl.gray()
        pl.title(title)
        pl.axis('off')

It works perfectly but I would like to have the option for plotting all the figures in single window. And this code doesn't. I read something about subplot but it looks quite tricky.

Answer 1

import numpy as np

def save_image(data, ws=0.1, hs=0.1, sn='save_name'):
    import matplotlib.pyplot as plt
    m = n = int(np.sqrt(data.shape[0])) # (36, 1, 32, 32)

    fig, ax = plt.subplots(m,n, figsize=(m*6,n*6))
    ax = ax.ravel()
    for i in range(data.shape[0]):
        ax[i].matshow(data[i,0,:,:])
        ax[i].set_xticks([])
        ax[i].set_yticks([])

    plt.subplots_adjust(left=0.1, bottom=0.1, right=0.9, 
                        top=0.9, wspace=ws, hspace=hs)
    plt.tight_layout()
    plt.savefig('{}.png'.format(sn))

data = np.load('img_test.npy')

save_image(data, ws=0.1, hs=0.1, sn='multiple_plot')

Answer 2

def plot_figures(figures, nrows=None, ncols=None):
    if not nrows or not ncols:
        # Plot figures in a single row if grid not specified
        nrows = 1
        ncols = len(figures)
    else:
        # check minimum grid configured
        if len(figures) > nrows * ncols:
            raise ValueError(f"Too few subplots ({nrows*ncols}) specified for ({len(figures)}) figures.")

    fig = plt.figure()

    # optional spacing between figures
    fig.subplots_adjust(hspace=0.4, wspace=0.4)

    for index, title in enumerate(figures):
        plt.subplot(nrows, ncols, index + 1)
        plt.title(title)
        plt.imshow(figures[title])
    plt.show()

Any grid configuration (or none) can be specified as long as the product of the number of rows and the number of columns is equal to or greater than the number of figures.

For example, for len(figures) == 10, these are acceptable

plot_figures(figures)
plot_figures(figures, 2, 5)
plot_figures(figures, 3, 4)
plot_figures(figures, 4, 3)
plot_figures(figures, 5, 2)

Answer 3

If you want to group multiple figures in one window you can do smth. like this:

import matplotlib.pyplot as plt
import numpy as np


img = plt.imread('C:/.../Download.jpg') # Path to image
img = img[0:150,50:200,0] # Define image size to be square --> Or what ever shape you want

fig = plt.figure()

nrows = 10 # Define number of columns
ncols = 10 # Define number of rows
image_heigt = 150 # Height of the image
image_width = 150 # Width of the image


pixels = np.zeros((nrows*image_heigt,ncols*image_width)) # Create 
for a in range(nrows):
    for b in range(ncols):
        pixels[a*image_heigt:a*image_heigt+image_heigt,b*image_heigt:b*image_heigt+image_heigt] = img
plt.imshow(pixels,cmap='jet')
plt.axis('off')
plt.show()

As result you receive:

Answer 4

You can also do this:

import matplotlib.pyplot as plt

f, axarr = plt.subplots(1, len(imgs))
for i, img in enumerate(imgs):
    axarr[i].imshow(img)

plt.suptitle("Your title!")
plt.show()

Answer 5

Building on the answer from: How to display multiple images in one figure correctly?, here is another method:

import math
import numpy as np
import matplotlib.pyplot as plt

def plot_images(np_images, titles = [], columns = 5, figure_size = (24, 18)):
    count = np_images.shape[0]
    rows = math.ceil(count / columns)

    fig = plt.figure(figsize=figure_size)
    subplots = []
    for index in range(count):
        subplots.append(fig.add_subplot(rows, columns, index + 1))
        if len(titles):
            subplots[-1].set_title(str(titles[index]))
        plt.imshow(np_images[index])

    plt.show()

Answer 6

You can define a function based on the subplots command (note the s at the end, different from the subplot command pointed by urinieto) of matplotlib.pyplot.

Below is an example of such a function, based on yours, allowing to plot multiples axes in a figure. You can define the number of rows and columns you want in the figure layout.

def plot_figures(figures, nrows = 1, ncols=1):
    """Plot a dictionary of figures.

    Parameters
    ----------
    figures : <title, figure> dictionary
    ncols : number of columns of subplots wanted in the display
    nrows : number of rows of subplots wanted in the figure
    """

    fig, axeslist = plt.subplots(ncols=ncols, nrows=nrows)
    for ind,title in enumerate(figures):
        axeslist.ravel()[ind].imshow(figures[title], cmap=plt.gray())
        axeslist.ravel()[ind].set_title(title)
        axeslist.ravel()[ind].set_axis_off()
    plt.tight_layout() # optional

Basically, the function creates a number of axes in the figures, according to the number of rows (nrows) and columns (ncols) you want, and then iterates over the list of axis to plot your images and adds the title for each of them.

Note that if you only have one image in your dictionary, your previous syntax plot_figures(figures) will work since nrows and ncols are set to 1 by default.

An example of what you can obtain:

import matplotlib.pyplot as plt
import numpy as np

# generation of a dictionary of (title, images)
number_of_im = 6
figures = {'im'+str(i): np.random.randn(100, 100) for i in range(number_of_im)}

# plot of the images in a figure, with 2 rows and 3 columns
plot_figures(figures, 2, 3)

Answer 7

You should use subplot.

In your case, it would be something like this (if you want them one on top of the other):

fig = pl.figure(1)
k = 1
for title in figures:
    ax = fig.add_subplot(len(figures),1,k)
    ax.imshow(figures[title])
    ax.gray()
    ax.title(title)
    ax.axis('off')
    k += 1

Check out the documentation for other options.